Prime Minister Naoto Kan told parliament that Japan was dealing with its worst problems since World War II.
"This quake, tsunami and the nuclear accident are the biggest crises for Japan" in decades said Kan. He said the crises remained unpredictable, but added: "We will continue to handle it in a state of maximum alert."
The magnitude-9.0 earthquake on March 11 triggered a tsunami that slammed minutes later into Japan's northeast, wiping out towns and knocking out power and backup systems at the coastal Fukushima Dai-ichi nuclear power plant.
The plant has been leaking radiation that has made its way into vegetables, raw milk and tap water as far away as Tokyo. Residents within 12 miles (20 kilometers) of the plant were ordered to leave and some nations banned the imports of food products from the Fukushima region.
Toxic plutonium was the latest contaminant found trickling out of that stricken nuclear plant. The plutonium has been detected in soil in several spots outside the complex.
Plutonium is a highly toxic substance which breaks down very slowly, remaining dangerously radioactive for hundreds of thousands of years.
Officials say the amounts are so small they are not a risk to humans. The discovery supports suspicions that radioactive water is leaking from damaged fuel rods.
The mission to stabilize the Fukushima plant has been fraught with setbacks.
Workers succeeded last week in reconnecting some parts of the plant to the power grid. But as they pumped water into units to cool the reactors down, they discovered pools of contaminated water in numerous spots.
The contaminated water has been emitting radiation exposures more than four times the amount the government considers safe for workers and must be pumped out before electricity can be restored to the cooling system.
That has left officials struggling with two crucial but sometimes-contradictory efforts: pumping in water to keep the fuel rods cool and pumping out contaminated water and safely storing it.
Following the twin disasters, police said more than 11,000 bodies have been recovered, but the final death toll is expected to exceed 18,000. Hundreds of thousands remain homeless, their homes and livelihoods destroyed. Damage could amount to $310 billion - the most expensive natural disaster on record, the government said.
The Associated Press contributed to this report.